Ethmoid bone - Human Anatomy FIG. 149 Ethmoid bone from above. (Os Ethmoidale) The ethmoid bone is exceedingly light and spongy, and cubical in shape; it is situated at the anterior part of the base of the cranium, between the two orbits, at the roof of the nose, and contributes to each of these cavities. It consists of four parts: a horizontal or cribriform plate, forming part of the base of the cranium; a perpendicular plate, constituting part of the nasal septum; and two lateral masses or labyrinths. Cribiform Plate (lamina cribrosa; horizontal lamina).The cribriform plate (Fig. 149) is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities. Projecting upward from the middle line of this plate is a thick, smooth, triangular process, the crista galli, so called from its resemblance to a cocks comb. The long thin posterior border of the crista galli serves for the attachment of the falx cerebri.

Its anterior border, short and thick, articulates with the frontal bone, and presents two small projecting alæ, which are received into corresponding depressions in the frontal bone and complete the foramen cecum. Its sides are smooth, and sometimes bulging from the presence of a small air sinus in the interior. On either side of the crista galli, the cribriform plate is narrow and deeply grooved; it supports the olfactory bulb and is perforated by foramina for the passage of the olfactory nerves. The foramina in the middle of the groove are small and transmit the nerves to the roof of the nasal cavity; those at the medial and lateral parts of the groove are largerthe former transmit the nerves to the upper part of the nasal septum, the latter those to the superior nasal concha. At the front part of the cribriform plate, on either side of the crista galli, is a small fissure which is occupied by a process of dura mater. Lateral to this fissure is a notch or foramen which transmits the nasociliary nerve; from this notch a groove extends backward to the anterior ethmoidal foramen. FIG.

150 Perpendicular plate of ethmoid. Shown by removing the right labyrinth. Perpendicular Plate (lamina perpendicularis; vertical plate).The perpendicular plate (Figs. 150, 151) is a thin, flattened lamina, polygonal in form, which descends from the under surface of the cribriform plate, and assists in forming the septum of the nose; it is generally deflected a little to one or other side. The anterior border articulates with the spine of the frontal bone and the crest of the nasal bones. The posterior border articulates by its upper half with the sphenoidal crest, by its lower with the vomer. The inferior border is thicker than the posterior, and serves for the attachment of the septal cartilage of the nose. The surfaces of the plate are smooth, except above, where numerous grooves and canals are seen; these lead from the medial foramina on the cribriform plate and lodge filaments of the olfactory nerves.

The Labyrinth or Lateral Mass (labyrinthus ethmoidalis) consists of a number of thin-walled cellular cavities, the ethmoidal cells, arranged in three groups, anterior, middle, and posterior, and interposed between two vertical plates of bone; the lateral plate forms part of the orbit, the medial, part of the corresponding nasal cavity. In the disarticulated bone many of these cells are opened into, but when the bones are articulated, they are closed in at every part, except where they open into the nasal cavity. Surfaces.The upper surface of the labyrinth (Fig. 149) presents a number of half-broken cells, the walls of which are completed, in the articulated skull, by the edges of the ethmoidal notch of the frontal bone. Crossing this surface are two grooves, converted into canals by articulation with the frontal; they are the anterior and posterior ethmoidal canals, and open on the inner wall of the orbit. The posterior surface presents large irregular cellular cavities, which are closed in by articulation with the sphenoidal concha and orbital process of the palatine. The lateral surface (Fig.

152) is formed of a thin, smooth, oblong plate, the lamina papyracea (os planum), which covers in the middle and posterior ethmoidal cells and forms a large part of the medial wall of the orbit; it articulates above with the orbital plate of the frontal bone, below with the maxilla and orbital process of the palatine, in front with the lacrimal, and behind with the sphenoid. FIG. 151 Ethmoid bone from behind. FIG. 152 Ethmoid bone from the right side. FIG. 153 Lateral wall of nasal cavity, showing ethmoid bone in position. In front of the lamina papyracea are some broken air cells which are overlapped and completed by the lacrimal bone and the frontal process of the maxilla. A curved lamina, the uncinate process, projects downward and backward from this part of the labyrinth; it forms a small part of the medial wall of the maxillary sinus, and articulates with the ethmoidal process of the inferior nasal concha. The medial surface of the labyrinth (Fig.

153) forms part of the lateral wall of the corresponding nasal cavity. It consists of a thin lamella, which descends from the under surface of the cribriform plate, and ends below in a free, convoluted margin, the middle nasal concha. It is rough, and marked above by numerous grooves, directed nearly vertically downward from the cribriform plate; they lodge branches of the olfactory nerves, which are distributed to the mucous membrane covering the superior nasal concha. The back part of the surface is subdivided by a narrow oblique fissure, the superior meatus of the nose, bounded above by a thin, curved plate, the superior nasal concha; the posterior ethmoidal cells open into this meatus. Below, and in front of the superior meatus, is the convex surface of the middle nasal concha; it extends along the whole length of the medial surface of the labyrinth, and its lower margin is free and thick. The lateral surface of the middle concha is concave, and assists in forming the middle meatus of the nose.

The middle ethmoidal cells open into the central part of this meatus, and a sinuous passage, termed the infundibulum, extends upward and forward through the labyrinth and communicates with the anterior ethmoidal cells, and in about 50 per cent. of skulls is continued upward as the frontonasal duct into the frontal sinus. Ossification.The ethmoid is ossified in the cartilage of the nasal capsule by three centers: one for the perpendicular plate, and one for each labyrinth. The labyrinths are first developed, ossific granules making their appearance in the region of the lamina papyracea between the fourth and fifth months of fetal life, and extending into the conchæ. At birth, the bone consists of the two labyrinths, which are small and ill-developed. During the first year after birth, the perpendicular plate and crista galli begin to ossify from a single center, and are joined to the labyrinths about the beginning of the second year. The cribriform plate is ossified partly from the perpendicular plate and partly from the labyrinths. The development of the ethmoidal cells begins during fetal life.

Articulations.The ethmoid articulates with fifteen bones: four of the craniumthe frontal, the sphenoid, and the two sphenoidal conchæ; and eleven of the facethe two nasals, two maxillæ, two lacrimals, two palatines, two inferior nasal conchæ, and the vomer. Sutural or Wormian (* 37 Bones.In addition to the usual centers of ossification of the cranium, others may occur in the course of the sutures, giving rise to irregular, isolated bones, termed sutural or Wormian bones. They occur most frequently in the course of the lambdoidal suture, but are occasionally seen at the fontanelles, especially the posterior. One, the pterion ossicle, sometimes exists between the sphenoidal angle of the parietal and the great wing of the sphenoid. They have a tendency to be more or less symmetrical on the two sides of the skull, and vary much in size. Their number is generally limited to two or three; but more than a hundred have been found in the skull of an adult hydrocephalic subject. Note 37.

Ole Worm, Professor of Anatomy at Copenhagen, 16241639, was erroneously supposed to have given the first detailed description of these bones. [ back ] II. Osteology. 5a. 6. Ethmoid bone. Gray, Henry. 1918. Anatomy of the Human Body. Henry Gray (18211865). Anatomy of the Human Body. 1918. (Os Ethmoidale) The ethmoid bone is exceedingly light and spongy, and cubical in shape; it is situated at the anterior part of the base of the cranium, between the two orbits, at the roof of the nose, and contributes to each of these cavities. It consists of four parts: a horizontal or cribriform plate, forming part of the base of the cranium; a perpendicular plate, constituting part of the nasal septum; and two lateral masses or labyrinths. 1 Cribiform Plate (lamina cribrosa; horizontal lamina).The cribriform plate (Fig. 149) is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities.

Projecting upward from the middle line of this plate is a thick, smooth, triangular process, the crista galli, so called from its resemblance to a cocks comb. The long thin posterior border of the crista galli serves for the attachment of the falx cerebri. Its anterior border, short and thick, articulates with the frontal bone, and presents two small projecting alæ, which are received into corresponding depressions in the frontal bone and complete the foramen cecum. Its sides are smooth, and sometimes bulging from the presence of a small air sinus in the interior. On either side of the crista galli, the cribriform plate is narrow and deeply grooved; it supports the olfactory bulb and is perforated by foramina for the passage of the olfactory nerves. The foramina in the middle of the groove are small and transmit the nerves to the roof of the nasal cavity; those at the medial and lateral parts of the groove are largerthe former transmit the nerves to the upper part of the nasal septum, the latter those to the superior nasal concha.

At the front part of the cribriform plate, on either side of the crista galli, is a small fissure which is occupied by a process of dura mater. Lateral to this fissure is a notch or foramen which transmits the nasociliary nerve; from this notch a groove extends backward to the anterior ethmoidal foramen. FIG. 149 Ethmoid bone from above. ( See enlarged image ) FIG. 150 Perpendicular plate of ethmoid. Shown by removing the right labyrinth. ( See enlarged image ) Perpendicular Plate (lamina perpendicularis; vertical plate).The perpendicular plate ( Figs. 150, 151 ) is a thin, flattened lamina, polygonal in form, which descends from the under surface of the cribriform plate, and assists in forming the septum of the nose; it is generally deflected a little to one or other side. The anterior border articulates with the spine of the frontal bone and the crest of the nasal bones. The posterior border articulates by its upper half with the sphenoidal crest, by its lower with the vomer.

The inferior border is thicker than the posterior, and serves for the attachment of the septal cartilage of the nose. The surfaces of the plate are smooth, except above, where numerous grooves and canals are seen; these lead from the medial foramina on the cribriform plate and lodge filaments of the olfactory nerves. 3 The Labyrinth or Lateral Mass (labyrinthus ethmoidalis) consists of a number of thin-walled cellular cavities, the ethmoidal cells, arranged in three groups, anterior, middle, and posterior, and interposed between two vertical plates of bone; the lateral plate forms part of the orbit, the medial, part of the corresponding nasal cavity. In the disarticulated bone many of these cells are opened into, but when the bones are articulated, they are closed in at every part, except where they open into the nasal cavity. 4 Surfaces.The upper surface of the labyrinth (Fig. 149) presents a number of half-broken cells, the walls of which are completed, in the articulated skull, by the edges of the ethmoidal notch of the frontal bone.

Crossing this surface are two grooves, converted into canals by articulation with the frontal; they are the anterior and posterior ethmoidal canals, and open on the inner wall of the orbit. The posterior surface presents large irregular cellular cavities, which are closed in by articulation with the sphenoidal concha and orbital process of the palatine. The lateral surface (Fig. 152) is formed of a thin, smooth, oblong plate, the lamina papyracea (os planum), which covers in the middle and posterior ethmoidal cells and forms a large part of the medial wall of the orbit; it articulates above with the orbital plate of the frontal bone, below with the maxilla and orbital process of the palatine, in front with the lacrimal, and behind with the sphenoid. FIG. 151 Ethmoid bone from behind. ( See enlarged image ) FIG. 152 Ethmoid bone from the right side. ( See enlarged image ) FIG. 153 Lateral wall of nasal cavity, showing ethmoid bone in position.

( See enlarged image ) In front of the lamina papyracea are some broken air cells which are overlapped and completed by the lacrimal bone and the frontal process of the maxilla. A curved lamina, the uncinate process, projects downward and backward from this part of the labyrinth; it forms a small part of the medial wall of the maxillary sinus, and articulates with the ethmoidal process of the inferior nasal concha. 6 The medial surface of the labyrinth (Fig. 153) forms part of the lateral wall of the corresponding nasal cavity. It consists of a thin lamella, which descends from the under surface of the cribriform plate, and ends below in a free, convoluted margin, the middle nasal concha. It is rough, and marked above by numerous grooves, directed nearly vertically downward from the cribriform plate; they lodge branches of the olfactory nerves, which are distributed to the mucous membrane covering the superior nasal concha.

The back part of the surface is subdivided by a narrow oblique fissure, the superior meatus of the nose, bounded above by a thin, curved plate, the superior nasal concha; the posterior ethmoidal cells open into this meatus. Below, and in front of the superior meatus, is the convex surface of the middle nasal concha; it extends along the whole length of the medial surface of the labyrinth, and its lower margin is free and thick. The lateral surface of the middle concha is concave, and assists in forming the middle meatus of the nose. The middle ethmoidal cells open into the central part of this meatus, and a sinuous passage, termed the infundibulum, extends upward and forward through the labyrinth and communicates with the anterior ethmoidal cells, and in about 50 per cent. of skulls is continued upward as the frontonasal duct into the frontal sinus. 7 Ossification.The ethmoid is ossified in the cartilage of the nasal capsule by three centers: one for the perpendicular plate, and one for each labyrinth.

8 The labyrinths are first developed, ossific granules making their appearance in the region of the lamina papyracea between the fourth and fifth months of fetal life, and extending into the conchæ. At birth, the bone consists of the two labyrinths, which are small and ill-developed. During the first year after birth, the perpendicular plate and crista galli begin to ossify from a single center, and are joined to the labyrinths about the beginning of the second year. The cribriform plate is ossified partly from the perpendicular plate and partly from the labyrinths. The development of the ethmoidal cells begins during fetal life. 9 Articulations.The ethmoid articulates with fifteen bones: four of the craniumthe frontal, the sphenoid, and the two sphenoidal conchæ; and eleven of the facethe two nasals, two maxillæ, two lacrimals, two palatines, two inferior nasal conchæ, and the vomer.

Sutural or Wormian 37 Bones.In addition to the usual centers of ossification of the cranium, others may occur in the course of the sutures, giving rise to irregular, isolated bones, termed sutural or Wormian bones. They occur most frequently in the course of the lambdoidal suture, but are occasionally seen at the fontanelles, especially the posterior. One, the pterion ossicle, sometimes exists between the sphenoidal angle of the parietal and the great wing of the sphenoid. They have a tendency to be more or less symmetrical on the two sides of the skull, and vary much in size. Their number is generally limited to two or three; but more than a hundred have been found in the skull of an adult hydrocephalic subject. The Ethmoid Bone - Anatomy, Borders and Development | Kenhub The Ethmoid Bone Contents The ethmoid bone is a singular porous bone that makes up the middle area of the viscerocranium and forms the midfacial region of the skull . It contributes to the moulding of the orbit , nasal cavity , nasal septum and the floor of the anterior cranial fossa.

Recommended video: Lacrimal bone Anatomy, function and definition of the lacrimal bone. Anatomy The bone consists of a perpendicular plate and two ethmoidal labyrinths parts which are all superiorly attached to the cribriform plate. A smaller orbital part extends towards the orbit. The ethmoid labyrinths lie on both lateral sides and contain numerous little cavities with ethmoidal cells which are referred to as the ethmoidal sinus. The labyrinths form two of the biggest structures in the nasal cavity: the superior and middle nasal concha. The hiatus semilunaris separates the ethmoid bulla and the uncinate process. It constitutes the connection between the frontal and maxillary sinuses to the anterior ethmoidal cells. The perpendicular plate is a thin lamina which runs horizontally from the cribriform plate. Inferiorly it attaches to the septal cartilage of the nose and hereby forms part of the nasal septum. The cribriform plate (Latin “cribriform” = perforated) lies within the ethmoidal notch of the frontal bone and forms the roof of the nasal cavity.

As the name suggests it comprises numerous openings through which the olfactory fibers from the nasal cavity pass through to the anterior cranial fossa. The falx cerebri is attached to the crista galli (Latin “crista galli” = crest of the cock), a small vertical protrusion on top of the plate. The olfactory bulbs lie on two grooves lateral to the crista galli. Borders Because of its central location within the skull the ethmoid bone comes in contact with 15 other skull bones . The most important borders are: anteriorly to the frontal bone, posteriorly with the sphenoid bone and inferiorly to the vomer and inferior nasal concha. Osseous Development The ethmoid bone ossifies completely by endochondral ossification. In newborns the labyrinths are relatively small and both the perpendicular and cribriform plates consists mainly out of cartilage. The latter start to ossify by the age of one and fuse with the labyrinths by the age of two to form a single ethmoid bone. Join us at kenhub.com today and gain access to an unlimited number of articles, illustrations, lectures and online interactive quizzes.

At kenhub we aim to make your anatomy experience as smooth as possible by keeping it light and fun without losing those essential details that make all the difference to your grades! Get me the rest of this article for free Create your account and you’ll be able to see the rest of this article, plus videos and a quiz to help you memorize the information, all for free. You’ll also get access to articles, videos, and quizzes about dozens of other anatomy systems. Show references References: Neil S. Norton, Frank H. Netter: Netter’s Head and Neck Anatomy for Dentistry, 2nd Edition, Elsevier Saunders, p. 38 Geoffrey H.

Sperber: Craniofacial development, BC Decker (2001), p.95 Friedrich Anderhuber, Franz Pera, Johannes Streicher: Waldeyer Anatomie des Menschen, De Gruyter (2012), 19th edition, p.721 Michael Schünke, Erik Schulte, Udo Schumacher: Prometheus Lernatlas der Anatomie - Kopf, Hals und Neuroanatomie, 2nd edition, Thieme (2009), p.37 Author: Ethmoid bone | definition of ethmoid bone by Medical dictionary Ethmoid bone | definition of ethmoid bone by Medical dictionary bone [bōn] 1. the hard, rigid form of connective tissue constituting most of the skeleton of vertebrates, composed chiefly of calcium salts. 2. any distinct piece of the skeleton of the body. See anatomic Table of Bones in the Appendices for regional and alphabetical listings of bones, and see color plates 1 and 2. Called also os . adj., adj bo´ny. There are 206 separate bones in the human body.

Collectively they form the skeletal system , a structure bound together by ligaments at the joints and set in motion by the muscles, which are secured to the bones by means of tendons. Bones, ligaments, muscles, and tendons are the tissues of the body responsible for supporting and moving the body. Some bones have a chiefly protective function. An example is the skull, which encloses the brain, the back of the eyeball, and the inner ear. Some, such as the pelvis, are mainly supporting structures. Other bones, such as the jaw and the bones of the fingers, are concerned chiefly with movement. The bone marrow in the center manufactures blood cells. The bones themselves act as a storehouse of calcium , which must be maintained at a certain level in the blood for the body's normal chemical functioning. Structure and Composition. Bone is not uniform in structure but is composed of several layers of different materials. The outermost layer, the periosteum, is a thin, tough membrane of fibrous tissue. It gives support to the tendons that secure the muscle to the bone and also serves as a protective sheath. This membrane encloses all bones completely except at the joints where there is a layer of cartilage.

Beneath the periosteum lie the dense, hard layers of bone tissue called compact bone. Its composition is fibrous rather than solid and it gives bone its resiliency. Encased within these layers is the tissue that makes up most of the volume of bone, called cancellous or spongy bone because it contains little hollows like those of a sponge. The innermost portion of the bone is a hollow cavity containing marrow. Blood vessels course through every layer of bone, carrying nutritive elements, oxygen, and other products. Bone tissue also contains a large number of nerves. The basic chemical in bone, which gives bone its hardness and strength, is calcium phosphate. Development. Cartilage forms the major part of bone in the very young; this accounts for the great flexibility and resiliency of the infant skeleton. Gradually, calcium phosphate collects in the cartilage, and it becomes harder and more brittle. Some of the cartilage cells break loose, so that channels develop in the bone shaft. Blood vessels enter the channels, bearing with them small cells of connective tissue, some of which become osteoblasts, cells that form true bone. The osteoblasts enter the hardened cartilage, forming layers of hard, firm bone.

Other cells, called osteoclasts, work to tear down old or excess bone structure, allowing the osteoblasts to rebuild with new bone. This renewal continues throughout life, although it slows down with age. Cartilage formation and the subsequent replacement of cartilage by hard material is the mechanism by which bones grow in size. During the period of bone growth, cartilage grows over the hardened portion of bone. In time, this layer of cartilage hardens as calcium phosphate is added, and a fresh layer grows over it, and it too hardens. The process continues until the body reaches full growth. Long bones grow in length because of special cross-sectional layers of cartilage located near the flared ends of the bone. These harden and new cartilage is produced by the same process as previously described. Bone Disorders. fracture , a break in the bone, is the most common injury to the bone; it may be closed, with no break in the skin, or open, with penetration of the skin and exposure of portions of the broken bone. osteoporosis is excessive brittleness and porosity of bone in the aged.

osteomyelitis is a bone infection similar to a boil on the skin, but much more serious because blood supply to bone is less exquisite than that to other body organs and bone metabolizes more slowly, so that the infection can destroy the bone and invade other body tissues. osteomalacia is the term used for rickets when it occurs in adults. In these diseases there is softening of the bones, due to inadequate concentration of calcium or phosphorus in the body. The usual cause is deficiency of vitamin D, which is required for utilization of calcium and phosphorus by the body. In osteitis fibrosa cystica , bone is replaced by fibrous tissue because of abnormal calcium metabolism. The condition usually is due to overactivity of the parathyroid glands. osteoma refers to abnormal new growth, either benign or malignant, of the tissue of the bones. Although it is not common, it may occur in any of the bones of the body, and at any age. alveolar bone the thin layer of bone making up the bony processes of the maxilla and mandible, surrounding and containing the teeth; it is pierced by many small blood vessels, lymphatic vessels, and nerves. wormian bone sutural bone .

zygomatic bone the quadrilateral bone that forms a cheek. See anatomic Table of Bones in the Appendices. eth·moid bone [TA] an irregularly shaped bone lying between the orbital plates of the frontal bone and anterior to the sphenoid bone of the cranium; it consists of two lateral ethmoidal labyrinths of thin plates enclosing air cells, attached above to a perforated horizontal lamina, the cribriform plate, from which descends a median, vertical, perpendicular plate in the interval between the two labyrinths; the bone articulates with the sphenoid, frontal, maxillary, lacrimal, and palatine bones, the inferior nasal concha, and the vomer; it enters into the formation of the anterior cranial fossa, the orbits, and the nasal cavity, forming the supreme, superior, and middle conchae of the latter. ethmoid bone (ĕth′moid′) n. A light spongy bone located between the eye sockets, forming part of the walls and septum of the superior nasal cavity, and containing numerous perforations for the passage of the fibers of the olfactory nerves.

ethmoid bone the very light, sievelike, and spongy bone at the base of the cranium, also forming the roof and most of the walls of the superior part of the nasal cavity. It consists of four parts: a horizontal plate, a perpendicular plate, and two lateral labyrinths. Ethmoid bone eth·moid bone (eth'moyd bōn) [TA] An irregularly shaped bone lying between the orbital plates of the frontal bone and anterior to the sphenoid bone; it consists of two lateral masses of thin plates enclosing air cells, attached above to a perforated horizontal lamina, the cribriform plate, from which descends a median vertical or perpendicular plate in the interval between the two lateral masses; the bone articulates with the sphenoid, frontal, maxillary, lacrimal, and palatine bones, the inferior nasal concha, and the vomer; it enters into the formation of the anterior cranial fossa, the orbits, and the nasal cavity. ethmoid bone The delicate, T-shaped, spongy bone forming the roof and upper sides of the nose and the inner walls of the eye sockets (orbits).

The upper part of the ethmoid is perforated (cribriform plate) to allow passage of the fibres of the olfactory nerve, and has a central downward extension forming the upper part of the partition (septum) of the nose. The bone contains numerous air cells (ethmoidal sinuses). orbit A rigid bony cavity in the skull which contains an eyeball, orbital fat, the extraocular muscles, the optic nerve, nerves and blood vessels, lacrimal system and fibrous tissue of various kinds. This packing serves to keep the eyeball reasonably well fixed in place as it rotates. The orbital cavity has the approximate form of a pyramid. The walls of the orbital cavity are formed by seven bones. The medial wall of the orbit consists of: (1) the frontal process of the maxilla (maxillary); (2) the lacrimal bone; (3) the lamina papyracea of the ethmoid; and (4) a small part of the body of the sphenoid.

The floor of the orbit consists of: (1) the orbital plate of the maxilla; (2) the orbital surface of the zygomatic (malar) bone and (3) the orbital process of the palatine bone. The lateral wall of the orbit consists of (1) the orbital surface of the greater wing of the sphenoid, and (2) the orbital surface of the zygomatic. The roof of the orbit is made up mainly by the frontal bone and behind this by the lesser wing of the sphenoid. The orbit is lined with a membrane of tissue called the periorbita (or orbital periosteum) which extends to the orbital margin (anterior rim of the orbit) where it becomes continuous with the periosteum covering the facial bones. The periorbita is loosely attached to the bones except at sutures, foramina and the orbital margin where it is firmly attached. The bones are much thicker at the margin (rim) than they are along the walls of the orbital cavity. There are many apertures and gaps in the orbit through which blood vessels and nerves pass (see Table O4).

See orbital axis ; optic canal ; inferior orbital fissure ; superior orbital fissure ; orbital fracture ; cavernous haemangioma ; lamina papyracea . Table O3 Bones forming the walls of the orbit roof Cranial and Facial Bones - Skeletal System Skeletal System 11 February 2016 - Lassa Fever outbreak in Benin, West Africa Bones of the Human Cranium and Face Introductory Note: Knowledge of bone structure and familarisation with the major bones of the human body is an essential part of training in many therapies, such as massage (in its many forms, incl. Indian head massage, Swedish massage, acupressure massage etc.), aromatherapy, shiatsu, and others. This page is intended to include the amount of detail required for most First Level Courses and some ITEC Diplomas. There are typically 206 bones in the body, though there may be up to about 226. Of these there are 22 bones of the Skull, which include: 8 Cranial Bones: 2 x Zygomatic Bones The other bone also included in this section is the hyoid bone, which is located in the neck (as illustrated below).

Other bones that may also be required knowledge to pass courses in Indian head massage and other similar therapies include: 33 Spinal Bones: 2 x Scapula 1 x Sternum The following two diagrams illustrate the positions of most of the cranial and facial bones required by First Level courses in massage and other therapies. It is not possible to illustrate all of the bones and parts of bones that may be included on such courses without also including more complicated diagrams illustrating sections cut through the skull (such as sagittal and transverse sections). To include information about the locations of all of the main features of the skeletal structures of the face and cranium, a table is included below the diagrams, summarising key facts about each. Diagrams of Cranial and Facial Bones Table Summarising Key Features of Cranial and Facial Bones (of skeletal structure of head) Orbit(s) Definition: The cavity (cavities) in the skull that contain the eye(s). These cavities are formed from parts of the following bones (also mentioned below): frontal, ethmoid, lacrimal, maxillary, palatine, sphenoid, and zygomatic.

Mechanical protection of the sensitive structures of the eye(s), including the eye balls themselves, together with the associated muscles, nerves, blood supply, and other tissues. Paranasal Sinuses Definition: air-filled cavities lined with mucous membranes located within some skull bones. Paranasal sinuses include: frontal sinuses and maxillary sinuses (one pair of each); ethmoid sinuses (many spaces inside the ethmoid bone); two sphenoid sinuses. These are named after the bones in which they are located - see diagram for positions of bones. Producing mucus; Acting as resonating chambers - resulting in personal speaking and singing sounds that differ from person to person. draining mucus out of the skull via the nasal cavities as necessary (e.g. in case of over-production of mucus). Sutures Definition: The word "suture" has meanings in both anatomy and surgery. In the context of anatomy, a 'suture' is a type of immovable joint found only between skull bones and consisting of a small amount of connective tissue between the bones.

There are several of these joints in the skull, examples include: Coronal Suture (between frontal and parietal bones); Lamboidal Suture (between the parietal and occipital bones); and Sagittal Suture (between the two parietal bones). These joints hold the bones of the skull together. Bones of the Cranium Floor of the cranium, inferior to the frontal bone and anterior to the sphenoid. Non-technically: Centre of the face, behind the nose. Forms part of the nasal cavity and the orbits. Main support structure of the nasal cavity Frontal Forehead, extending down to form the upper surfaces of the orbits. Anterior roof of the skull. Back and base of the cranium, forms the back of the skull. Non-technically: Lower back of the head. The occipital condyles (rounded surfaces at the base of the occipital bone) articulate with the atlas (first vertebra of the spine), enabling movement of the head relative to the spine. Has a large opening called the Foramen Magnus which the spinal cord passes through. Parietal Top and sides of the cranium, posterior roof of the skull.

Sphenoid Anterior to the temporal bones and forms the base of cranium - behind the orbitals. Consists of a body, two "wings" and two "pterygoid processes" (not labelled on diagrams) that project downwards. Articulates with the frontal, parietal and temporal bones. Temporal Sides of the skull, below the parietal bones, and above and behind the ears Bones of the Face Hyoid In the neck, below the tongue (held in place by ligaments and muscles between it and the styloid process of the temporal bone). Supports the tongue, providing attachment sites for some tongue muscles, and also some muscles of the neck and pharynx. (Commonly fractured during strangulation, so studied in autopsies if strangulation suspected.) Lacrimal Behind and lateral to the nasal bone, also contribute to the orbits. (Smallest bones in the face.) Contain foramina for the nasolacrimal ducts (tear ducts). Mandible Known as the lower jaw bone. Also forms the chin and sides of the face. (Largest, strongest facial bone.) Bone into which the lower teeth are attached.

The only moveable facial bone; motion of this bone is necessary for chewing food (the first stage of the digestion process). Each side of the mandible has a condyle and a coronoid process. The condyle articulates with the temporal bone to form the temporomandibular joint. Maxilla Upper jaw bone, which also forms the lower parts of the orbits. Bone into which the upper teeth are attached. Each maxilla contains a maxillary sinus that drains fluid into the nasal cavity. Nasal Pair of small oblong bones that form the bridge and roof of the nose. Palatine Back of the roof of the mouth (hence not illustrated above). Small "L-shaped" bones. Form the bottom of the orbitals and nasal cavities, and also the roof of the mouth. Turbinator Also known as Turbinate Bone and Nasal Concha. These terms refer to any of three thin bones that form the sides of the nasal cavity (not illustrated in the diagrams above). Form the nasal cavities. Vomer Thin roughly triangular plate of bone on the floor of the nasal cavity and part of the nasal septum. Separates the nasal cavities into left and right sides. Zygomatic Supports and balances the head.

Allows flexion and extension of the head. Axis The second vertebra, immediately below the atlas. See diagram above. Allows rotation of the head. Clavicle Long bone(s) positioned in an approximately horizontal orientation between the base of the neck and the shoulders. Forms the anterior aspect of the shoulder girdle and is sometimes (non-medically) referred to as the "collar bone". Articulates with the sternum (medially) and the scapulae (laterally). Humerus Long bone located in upper-arm (the longest bone in the upper-skeleton) Providing the mechanical structure of the upper-arms. Articulates with the scapula, enabling movement of the arms at the shoulder joints. Scapula Large, flat, triangular bones that form the posterior shoulder girdle (one scapula is located on each side of the body). Providing mechanical structure for the upper-body. Articulates with the clavicle and humerus, enabling movement of the arms at the shoulder joints. Sternum

Question: Where in the human body is the Ethmoid bone?
Answer: SKULL